Power transmission having a plural pump fluid pressure source and a flow-regulating diverting valve



Aprll 22,1947. R SHARTLE 2,419,375

POWER TRANSMISSION HAVING A PLURAL PUMP FLUID PRESSURE SOURCE AND AFLOW-REGULATING' DIVBRTING VALVE' Filed .June 29, 1942 2 Sheets-Sheet lnvvazvz'on ROBERT A. SHARTLE ATTORNEY Apiil 22.'-1947.

. R. A. SHARTLE POWER TRANSMISSION HAVING A PLURAL PUMP FLUID PRESSURESOURCE AND A FLOW-REGULATING DIVERTI'NG VALVE Filed June 29, 1942 2sheets-sheet 2 INVENTOR ROBERT A.SHARTLE BY M ATTQRNEY Patented Apr. 22,1947 A POWER TRANSMISSION HAVING A PLURAL PUMP FLUID PRESSURE SOURCE ANDA FLOW-REGULATING DIVERTING VALVE Robert A. Shartle, Rockford, 111.,assignor to Vickers Incorporated, Detroit, Mich., a corpora tion ofMichigan Application June 29, 1942, Serial No. 448,896

The invention is more particularly concerned with a hydraulic system foroperating an alternately reversing slide such as are found on ma- Ichine tools and which require the maintenance of a controlled butvariable feeding rate.

In applications of hydraulic drives to some machin tools, for example,to a planer, the wide range of feed rates which must be covered and thelarge amount of power involved has heretofore required the useof theexpensive variable stroke type of pumping mechanism for commerciallysuccessful machines. The difference in cost between a variable strokepump and a. fixed displacement pump of equal rating is'very great, andthe variable displacement pump has for this reason been excluded fromapplication to machines the sale of which is highly competitive.Accordingly, machines of this class have heretofore been denied theadvantages of hydraulic drive because none was available which wouldcompete on a cost basis with previous mechanical drives for the samepurpose.

It is an object of the present invention to provide an improvedhydraulic power transmission system providing substantially all theadvantages of a variable displacement system and which may be producedat a fraction of the cost of such a system.

Further objects and advantages of the present invention will be apparentfrom the following description, reference being had to the accompanyingdrawings wherein 'a preferred form of the present invention is clearlyshown.

In the drawings:

Figure 1 is a diagrammatic view of a power transmission systemincorporating a preferre form of the present invention.

Figures 2 and 3 illustrate the difierent operating positions of'acontrol valve of Figure 1.

Figures 4, 5 and 6 are schematic views of the circuit showing thposition of valves in various stages of the operating cycle.

In the embodiment of the invention shown in Figure 1, the circuitcomprises a pair of pumps II and [2 adapted to be driven by a suitableprime mover, such as an electric motor i 4. Pumps i0 and 12 are providedwith integral relief valves IB and i8 which limit the pressure thereinto a predetermined maximum by discharging the excess pressure to a tankthrough conduits 22 and 24, respectively. Fluid is withcylinder motor98.

. 2 which extends to the tank 20. passing through a check valve 32.

Pumps I 0 and i2 are provided with delivery conduits 34 and 36 whichextend to ports 18 and 40, respectively, of a reverse valve 42, conduit36 passing through a pressure responsive valve 44. Briefly, the lattercomprises a spool 46 spring biased downwardly to cut oil? port 48thereof from port ill. Valve 44 is directly operated by pressure in port50 thereof which acts on plunger 52 through passage 54. The spool 48 iscaused to rise, connecting ports 48 and Eli whenever the pressure inport 50 equals the valve spring adjustment. Port 55 of valve 44 is incontinuous communication with port 50, irrespective of the position ofthe spool 46. Valve 44 is externally drained by a conduit Sit-whichconnects with a tank conduit 60.

Valve 42, as shown, is of the spring-centered, pilot-operated typehaving the end lands of its spool 62 notched so as to connect ports 38and 40 with ports 84 and 66, respectively, when in its centered position(Figure 3). Port 68 of valve 42 is connected to a conduit 10 whichcommunicates with a conduit I2 and serves as a return conduit for thework circuit. Ports 64 and 66 are joined by a conduit 14 which connectswith a conduit l6. The latter communicates with a conduit I8 whichconnects the pressure ports of a reversing valve an and a start-and-stopvalve 82, respectively.

Valve is of the four-way, pilot-operated type containing small throttlesand check valves in both end caps 64 and 86 to restrict th liquiddischarge from the pilot valves and thus slow down the speed of thespool 88. Port 90 of valve 80 is plugged, while port 92 connects to aconduit 94 which leads to the head end oi. a piston-and- Conduit 94 hasa branch conduit 98 extending to a check valve me which prevents fluidflow therefrom.

The end or tank ports of valve 80 communicate through conduit )2 withthose of valve 82.

The latter is of the manually-operated type and ;contains aspring-pressed deten't M4 to maintain it in its two" effective operatingpositions. Port I05 of valve 82 connects to the conduit 12 which extendsto the suction side of the pumps l0 and i2 and also communicates withthe tank 20 through a pressure responsive valve Hi8 and a conduit we.Valve )8 is of similar construction and operation to that of valve t lhereinbefore described. Valve I08 interrupts the fluid flow to tankuntil a predetermined pressur is reached, thus maintaining a backpressure in conduit 12.

From port ill! of start-and-stop valve 82, a conduit 2 extends to therod end of the piston-and-cylinder motor 96, passing through a reliefvalve H4. The latter is adapted to maintively, so that the valve I20 iscaused to open or close the required amount to maintain a constantpressure drop through the oriflceJIB irrespective of pressure variationsat the port I24.

Piston-and-cylinder motor 96 is of the diflerential type, preferablywith a two-to-one ratio, and is adapted to actuate a slide, such as aplaner table I26, carrying stock thereon past a stationary cutter I28.Reciprocating slide I26 carries adjustable cams I30 and I32 to determineits stroke length by actuating a four-way, rotary pilot valve I34. Thelatter has its cylinder ports connected to conduits I36 and I38 whichlead to either pilot pressure chamber of the reversing.

valve 80. Conduits I36 and I38 have branch conduits I40 and I42,respectively, which extend to the rod and head ends of a cross-feedcylinder I44 which is adapted to move, by means of a feed pawl I46, thecutting tool I28 across the work. The tank port of rotary valve I34 isconnected to the conduit 60, while the pressure port thereof isconnected to a conduit I60 which leads to the port 56 of the pressureresponsive valve 44.

Conduit I36 extends beyond the righthand pilot chamber of valve 80 to aport I 50 of a rotary three-way valve I52. Port I 56 of the latter is incommunication with pressure conduit I46 through conduit I66, while portI56 thereof communicates through conduit I 66 with a port I62 of arotary pilot valve I66. The latter has its two cylinder ports connectedto conduits I66 and I68 which extend to either pilot pressurechamaeiasvs the remainder to the tank 20 through valve I03,

64, valve 66, conduit I02, valve 82 and into conduit I2. The latterdirects some of the discharging fluid tothe suction side of the pumpsand It will be seen that pump ID at this time is caused to discharge totank through conduit 34, valve 42, conduits I0 and I2, valve I06 andconduit I06.

At the end of the feed stroke, cam I32 of slide I26 will move rotaryvalve I34 to connect conduits I46 and I36 and conduits I36 and 60 tothereby shift valve 80 and also to operate the cross-feed cylinder I44.Conduit I36, now open to tank, causes valve 42 to center, the latterexpelling fluid through conduit I66, valve I64, conduit I60, valve I52and into conduit I36 where it flows to tank with the discharging fluidfrom valve 60.

With the centering of valve 42, the delivery conduits 34 and 36 of pumpsI0 and I2, respectively, become connected to conduit I4 as hereinbeforedisclosed. The respective pump deliver ies now combine to form a totaldelivery which is directed through conduit I6 into conduit I6. As spool80 of valve 60' is now to the right, conduit I8 is connected to conduit94, thus connecting the head and rod ends of the motor 66. The latter isnow caused to operate as a differential cylinder with the dischargingfluid from the right end traversing conduit II2, valve 02 and intoconduit 18, as shown diagrammatically in Figure 6. Upon reaching the endof its stroke, cam I30 on slide I26 will shift valve I34 to the positionshown in Figure 1 to again condition conduit I36. In this mannerconstant pilot prestwo positions, is arranged to-selectively connecteither conduit I36 or conduit I56 with conduit I66. Valve I66, manuallyoperated between three positions, is arranged to selectively transposeconduits I66 and I66 with respect to conduit I66 and conduit I10 andalso to connect the cylinder ports to the tank port.

In operation, with the parts in the position shown in Figure l, thecircuit is conditioned for repeated cycles of slow feed and rapid returnand is in the course oi a slow feeding movement. The pilot pressurehaving traversed conduit I63, valve I34, conduit I36, valve I 62,conduit I60, valve I66 and conduit I66 to shift the valves 66 and 42 tothe position shown, the delivery of small pump I2 is now directedthrough sequence valve 44 and valve 42 into conduit 16, thence throughconduit 16 to conduit I8. As the latter leads to a plugged port of valve80, the fluid fiow is directed through valve 82, conduit H2 and to therod end of motor 36. The rate of fluid flow therein is determined by thesetting of the flow control valve H6 as the latter bleeds off apredetermined volume from the known volume delivered by pump I2. Thisexcess volume passes through conduit III, check valve I60 and intoconduit 98 where it combines with the discharging fluid from the headend of motor 96. This combined flow is now directed through conduit surein conduit I is used to maintain the valve 42 in its shifted positionwithout centering regardless of the shifting of valve I34. Thus, if thesmall pump is used for the feed stroke, it alone will be used for thereturn stroke.

To obtain a medium feed rate, valve I64 is I shifted to connect conduitsI60 and I66 and conduits I66 and I'III to shift spool 62 of valve 42 tothe extreme left, as shown in Figure 2. This will render inoperative thesmall pump I2 by causing it to discharge to tank, and connect the largepump III with the working circuit. For a high feed rate, valve I64 isshifted to connect conduits I66 and I66 with the tank conduit III! andblocking conduit I60, as shown in Figure 3. This will cause valve 42 tocenter to direct the delivery of both pumps into conduit I4. It will beunderstood that these feed rates may be utilized, with the remainder ofthe circuit being the same as that described above for the slow feedrate, the only variation being in the position of valve 42. The feedrate may be gradually varied by increasing or decreasing the amount offluid bled" off from line H2, and it will be noted that valve I I6 needonly be large enough to carry the volume delivered by the small pump I2in order to obtain any feed rate from zero up to full capacity of bothpumps.

To stop the slide I 26 while in its cutting or feed .stroke, valve 62 isshifted to connect conduit II .with conduit I2 and conduit II2 withconduit I02. This will cause the pump or pumps to circulate fluid at noappreciablepressure by directing the fluid flow to the suction sidethereof, as shown in Figure 4. Simultaneously, oil discharging from thehead end of motor 96 will be directed through conduit 94, valve 89,conduit I02, valve 82 and conduit H2 to the rod end of motor 98. Astwice the amount of oil is being discharged as can be accommodated, theslide I26 will immediately stop, the relief valve Ill absorbing theshock caused by the inertia thereof.

During the return stroke, with valve spool 88 of valve 89 shifted to theright, connecting conduit 78 with conduit 94 and blocking either end ofconduit I02, to-stop the slide I25, valve 82 is shifted to the left,connecting conduits I8 and I2 and conduits I02 and H2 as best shown inFigure 5. This will cause the pump or pumps to again circulate fluid atno appreciable pressure. Simultaneously, the fluid discharging from therod end of motor 96 is directed through conduit H2, valve 82 and intoconduit I02. As the latter is connected to blocked ports of either valve80 and 82, the slide I26 is caused to stop, the relief valve againabsorbing the shock by discharging any excess pressure into conduit 10.

Thus it will be seen that the present invention provides a means fordriving a reciprocating mechanism and stopping the same promptly ineither directionyutilizing a relatively simplified circuit incorporatinga relief valve'which limits the working pressure and also acts as asafety device during the braking operation, relieving excess pressurecaused by the inertia of the slide.

While the form of embodiment of the invention as herein-disclosedconstitutes a preferred form, it is to be understood that other formsmight be adopted, all coming within the scope of the claims whichfollow.

What is claimed is as follows:

1. In a hydraulic power transmission system the combination of a fluidmotor operable at variable rates of speed. a source 01' pressure fluidfor supplying fluid to said motor and comprising a plurality of fixeddisplacement pumps, each having a different displacement, a deliveryline extending between the source and the motor, a selector valve forselectively rendering various pumps and combinations of pumps efl'ectiveto deliver fluid to the motor, and means for gradually varying the speedof the motor comprising a pressure-compensated,- flow-regulating valveconnected to the delivery line for causing a diversion of a variableportion of the fluid delivered having a range of flow rate adjustmentfrom zero up to and not substantially greate than the delivery of thesmallest pump, the large pump being twice the size of the small pumpwhereby the motor may be operated at any speed up to that of the totalcapacity of the source.

3. In a hydraulic power transmission system the combination of a fluidmotor operable at variable rates of speed, a source of pressure fluidfor supplying fluid to said motor and comprising a plurality of fixeddisplacement pumps, each having a different displacement, a deliveryline extending between the source and the motor. a selector valve forselectively rendering various pumps and combination of pumps eflectiveto deliver fluid to the motor, and means for gradually varying the speedof the motor comprising a valve connected to the delivery line fordiverting a predetermined proportion of the fluid delivered by thesource, said valve having a range of flow rate adjustment from zero upto and not substantially greater than the delivery of the smallest pump,said pumps differing in size by a multiple of the size of the smallestpump whereby the motor may be operated at any speed up to that of thetotal capacity of the source.

4. In a hydraulic power transmission system for operating an alternatelyreversing slide movable through feed advance and rapid return strokes,the combination of a differential piston-and-cyl inder motor connectedto operate the slide through its advance stroke by pressure applied tothe smaller area thereof, a source of pressure fluid comprising aplurality of fixed displacement from the source, said valve having arange of a flow rate adjustment from zero up to and not substantiallygreater than the delivery of the smallest pump, said pumps differing insize by a multiple of the size of the smallest pump whereby the motormay be operated at any speed up to that of the total capacity of thesource.

2. In a hydraulic power transmission system the combination of a fluidmotor operable at variable rates of speed, a source of pressure fluidfor supplying fluid to said motor and comprising a differentdisplacement, a delivery line extending between the source and themotor, a'selector valve for selectively rendering either or both a pairof fixed displacement pumps, each having pumps effective to deliver.fluid to the motor, and

pumps selectively connectable alone or in parallel to supply said motor,means for reversing the flow to the motor to cause a return stroke, andmeans operable concurrently with said reversing means for connectingsaid pumps in parallel to supply the maximum delivery during the returnstroke. I i

5. In a hydraulic power transmission system for operating an alternatelyreversing slide movable through feed' advance and rapid return strokes,the combination of ,a differential piston- REFERENCES CITED Thefollowing references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,932,760 west Oct. 31, 19332,288,830 Nye July 'I, 1942 1,848,006 Ferris Mar. 1, 1932 1,982,711Vickers Dec, 4, 1934 FOREIGN PATENTS Number Country Date British ::Nov.19, 1928

